British Journal of Anaesthesia 1994; 73: 247-248
The sitting position in neurosurgical anaesthesia: a survey of British
practice in 199If
R. J. ELTON AND R. S. C. HOWELL
SUMMARY
A postal survey of 160 members of the Neurosurgical Anaesthetists' Travelling Club was conducted in 1991 to investigate the current use of the
sitting position in neurosurgery. There was a 78%
response rate; at least one reply was received from
every neurosurgical centre in the UK. Patients were
placed normally in the sitting position for posterior
fossa surgery in eight (20%) of the centres,
compared with 19 (53%) in 1981. For posterior
cervical spinal surgery, only three (7%) centres
routinely used the sitting position, compared with
11 (31%) in 1981. Thus in the period 1981-1991,
the number of neurosurgical centres using the
sitting position routinely, decreased by more than
50%. Current techniques of ventilation and monitoring for the sitting position are discussed briefly.
(Br. J. Anaesth. 1994; 73: 247-248)
KEY WORDS
Anaesthesia: neurosurgical. Position, effects. Position: sitting
The use of the sitting position for patients undergoing posterior fossa and cervical spinal surgery
represents a unique physiological challenge and is
associated with several important complications.
In 1981, Campkin [1] reported that 19 (53%) of the
36 neurosurgical centres in the UK always used the
sitting position for posterior fossa surgery and 11
(30%) always used it for posterior cervical spinal
surgery. We set out to establish the extent of the use
of the sitting position in the UK in 1991 and to
compare this with the situation in 1981.
METHODS AND RESULTS
At the end of 1991 we mailed a questionnaire with a
reply paid envelope to all 160 members of the
Neuroanaesthetists' Travelling Club, a UK society,
the members of which have a major interest in the
practice of anaesthesia for neurosurgery (the club
has since been renamed the Neuroanaesthesia Society of Great Britain and Ireland). The respondents
were asked to specify which position they currently
used for patients undergoing posterior fossa or
posterior cervical surgery, if they used spontaneous
respiration or intermittent positive pressure ventilation (IPPV) and which monitoring techniques
were used.
We received 124 replies, a response rate of 78%,
of which 109 replies were returned fully completed,
68 % of the original mailing. Replies were received
from 41 centres, including all 39 in the UK and one
each in Ireland and Hong Kong, which have been
included in the analysis as they were considered to be
representative of British practice. It was noted that
24 (15%) of the Club's members were not anaesthetists and that the non-responders were mainly
from this group: we decided that as this questionnaire was not relevant to these individuals, it
would be acceptable to proceed to analyse and draw
conclusions from the questionnaires returned.
From the replies the respondents were divided
into three groups: (1) those who always used the
sitting position; (2) those who always used other
positions (prone or lateral) and never used the sitting
position; (3) those who used any of the three
positions, including the sitting position. As each
anaesthetist's practice was usually the same as the
others in the same centre, we aggregated the
responses into their respective centres to facilitate
close comparison with the situation in 1981. The chisquare test was used for statistical comparison
between groups. P < 0.05 was considered statistically significant.
The results are summarised in table I. Compared
with 1981, there was a significant reduction in the
TABLE I. Patient pojttions used m neurosurgical centres for posterior
fossa surgery and posterior cervical surgery m 1981 and 1991.
* P < 0 05, ** P < 0.01 compared tvith 1981
Sitting
posiuon
always
(" (%))
Posterior fossa surgery
1981
19 (53)
1991
8 (20)**
Posterior cervical surgery
1981
11(31)
3(7)*
1991
Other
positions
always
(" (%))
13 (36)
22 (54)
17(47)
31 (76)**
All
three
positions
(« (%))
4(11)
11 (27)**
8(22)
7(17)
Total
centres
36
41
36
41
R. J. ELTON, M.B., CH.B., F.R.C.A., R. S. C. HOWELL, M.B., B.S.,
D.OBST., R.C.O.G., F.R.C.A., Departments of Anaesthetics and
Neurosurgery, Walsgrave Hospital, Coventry, West Midlands
CV2 2DX. Accepted for Publication: February 22, 1994.
tThis paper was presented at the Registrars' Prize Meeting of
the Midland Society of Anaesthetists in Birmingham in March
1992 and an abstract was published in the Midland Society of
Anaesthetists Newsletter for Summer 1992. The data shown in
the paper were used in a poster presentation at the Combined
Meeting of the Neurosurgical Anaesthetists' Travelling Club and
the American Society of Neurosurgical Anaesthesia and Critical
Care in London, June 1992.
BRITISH JOURNAL OF ANAESTHESIA
248
number of centres which always used the sitting
position for posterior fossa surgery and a significant
increase in the use of the other positions. There was
a significant reduction in the use of the sitting
position for posterior cervical surgery. Several
respondents commented that although the sitting
position was retained as an option in their centres
(i.e. the group which used all three positions), it was
used only very occasionally.
Among the 21 anaesthetists who routinely used
the sitting position, 18 (86%) always used IPPV;
one respondent (5%) used spontaneous respiration
for posterior fossa surgery and two (10 %) used it for
posterior cervical surgery.
Among the 21 anaesthetists who always used the
sitting position, all (100%) used an electrocardiogram, pulse oximeter and end-tidal carbon dioxide
measurements and all but one (95%) used direct
arterial pressure measurement. Fourteen (67 %) used
a right atrial catheter, 13 (62%) a Doppler ultrasound probe over the precordium and 12 (57 %) used
an oesophageal stethoscope, in addition to the other
monitors; two (10%) of these anaesthetists also used
pulmonary artery catheters, one (5 %) used auditory
evoked potentials and one (5%) routinely measured
arterial pressure with an oscillotonometer only.
COMMENT
The advantages of the sitting position are entirely
surgical, in that it facilitates surgical access to some
parts of the posterior fossa and can also lead to a
reduction in the amount of venous bleeding during
surgery. The disadvantages [2-4] are that the
associated subatmospheric pressure in the veins at
the base of the skull may encourage venous air
embolism and that arterial hypotension may lead to
a disproportionate reduction in cerebral blood flow
because of the gravitational effect of the vertical
distance between the heart and the head. The
potential complications of neurosurgery and of the
sitting position in particular, have always made it
appropriate to use extensive monitoring [2]. The
standard equipment used by nearly all our respondents included an electrocardiogram for detecting rhythm disturbance, capnography with trend
recording as a measure of adequate ventilation and
an early detector of venous air embolism, intraarterial pressure for continuous accurate recording
of arterial pressure and prompt detection of hypotension, and pulse oximetry as a indication of
arterial oxygenation. Some of the additional monitoring techniques used for diagnosis and management of air embolism include Doppler ultrasound
probe applied to the precordium and an oesophageal
stethoscope. A catheter placed into the right atrium
allows aspiration of an air embolism [5].
ACKNOWLEDGEMENTS
We thank Dr J. Jenkinson, the Honorary Secretary of the
Neurosurgical Anaesthetists' Travelling Club and Dr M. C.
Clapham, Solihull Hospital, for statistical advice.
REFERENCES
1. Campkin TV. Posture and ventilation during posterior fossa
and cervical operations. Current practice in the United
Kingdom. British Journal of Anaesthesia 1981; 53: 881-884.
2. Broderick PM. The sitting position: monitoring, diagnosis
and treatment of air embolism. In: Jewkes DA, ed. Balltire's
Clinical Anaesthesiology, Volume 1, no. 2: Anaesthesia for
Neurosurgery. London: Balliere Tindall, 1987; 419-440.
3. Shapiro HM, Drummond JC. Neurosurgical anesthesia and
intracranial hypertension. In: Miller RD, ed. Anesthesia, 3rd
Edn. New York: Churchill Livingstone, 1990; 1737-1789.
4. Cucchiara RF. Safety of sitting position. Anesthesiology 1984;
61: 790.
5. Bedford RF, Marshall WK, Butler A, Welsh JE. Cardiac
catheters for diagnosis and treatment of venous air embolism.
A prospective study in man. Journal of Neurosurgery 1981;
55: 610-614.